1. FIELD OF THE INVENTION
This invention relates to the manufacture of patterned glass.
2. DESCRIPTION OF THE PRIOR ART
Glass manufacturing methods are known in which a metallic or coloured surface appearance is imparted to a glass surface by ionic migration of one or more metals from a molten metal body in contact with the glass surface to be treated, under the influence of a controlled electric current passing from the molten body into the glass. Surface modified float glass has been produced in this way.
Usually the molten metal body is located on the upper surface of an advancing ribbon of glass by clinging to the underface of an electrically conductive locating member fixed above the upper surface of the ribbon. The configuration of the underface of the locating member determines the configuration of the molten metal body. By maintaining a rectangular elongated form for the molten metal body uniform treatment of the ribbon surface across its whole usable width is achieved.
Shaded characteristics, transversely of the ribbon, have been produced, for example for the manufacture of glass for shaded windscreens, by using a shaped locating member tapering from the centre towards the ends of the member so that the molten metal body clinging to the underface of that member has a larger dimension, in the direction of ribbon advance, at the centre of the ribbon than at the margins of the ribbon.
It has also been proposed to produce shaded characteristics longitudinally of a ribbon of glass advancing along a molten metal bath by continuously varying the voltage applied to the molten metal body and so continuously varying the intensity of surface modification of the glass.
It is a main object of the present invention to develop these techniques for the production of patterned glass, particularly patterned float glass, having a decorative pattern introduced into a surface of the glass.